Magnetic angle sensor device and method of operation

ABSTRACT

A magnetic angle sensor device and a method for operating such device is provided. The magnetic angle sensor device includes a shaft rotatable around a rotation axis; a magnetic field source coupled to the shaft; a first magnetic angle sensor configured to generate a first signal that represents a first angle based on a first diametric magnetic field from the magnetic field source applied to the first magnetic angle sensor; a second magnetic angle sensor configured to generate a second signal that represents a second angle based on a second diametric magnetic field from the magnetic field source applied to the second magnetic angle sensor; and a combining circuit configured to determine a combined rotation angle based on the first signal and on the second signal.

FIELD

The present disclosure relates generally to a magnetic angle sensorarrangement, and more particularly, to a magnetic angle sensor deviceconfigured to determine a rotational position or movement of a shaft anda method of operation.

BACKGROUND

A magnetic angle sensor may be used to detect a rotational position ormovement of a shaft. Typically, a permanent magnet is attached to arotatable shaft and a single magnetic field sensor is placed on therotation axis and adjacent to the magnet.

A disadvantage of known solutions is that they are very sensitive tomagnetic disturbances. For example, if the magnet generates a field of,e.g., 45 mT at the sensor elements, a magnetic disturbance amounting to,e.g., 3 mT (in a worst case direction perpendicular to the axis andorthogonal to the field of the magnet) leads to an error amounting to3.8° (arctan(3/45)=)3.8°, which is generally not acceptable.

SUMMARY

Embodiments provided herein relate to a magnetic angle sensorarrangement that determines a rotational position or movement of ashaft.

According to one or more embodiments, a magnetic angle sensor deviceincludes: a shaft rotatable around a rotation axis; a magnetic fieldsource, where the magnetic field source is connected to the shaft; afirst magnetic angle sensor; and a second magnetic angle sensor. Thefirst magnetic angle sensor is configured to determine a first signalthat represents a first angle based on a first diametric magnetic fieldapplied to the first magnetic angle sensor, and the second magneticangle sensor is configured to determine a second signal that representsa second angle based on a second diametric magnetic field applied to thesecond magnetic angle sensor. A combining circuit is configured todetermine a combined rotation angle based on the first signal and on thesecond signal.

According to one or more embodiments, a method for determining acombined rotation angle of a shaft using a magnetic angle sensor deviceis provided. The magnetic angle sensor device includes a shaft rotatablearound a rotation axis, a magnetic field source connected to the shaft,a first magnetic angle sensor, and a second magnetic angle sensor. Themethod includes determining by the first magnetic angle sensor a firstsignal that represents a first angle based on a first diametric magneticfield applied to the first magnetic angle sensor; determining by thesecond magnetic angle sensor a second signal that represents a secondangle based on a second diametric magnetic field applied to the secondmagnetic angle sensor; and determining the combined rotation angle basedon the first signal and on the second signal.

According to one or more embodiments, a computer program productdirectly loadable into a memory of a digital processing device,including software code portions that enable the digital processingdevice to perform one or more methods described herein.

According to one or more embodiments, a computer-readable medium, e.g.,non-transitory storage of any kind, is provided havingcomputer-executable instructions adapted to cause a computer system toperform one or more methods described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are shown and illustrated with reference to the drawings.The drawings serve to illustrate the basic principle, so that onlyaspects necessary for understanding the basic principle are illustrated.The drawings are not to scale. In the drawings the same referencecharacters denote like features.

FIG. 1 shows an example embodiment of a sensor system including a shaftthat rotates around a rotation axis, where a magnet is attached to theshaft and rotates above three magnetic angle sensors that are arrangedon the rotation axis;

FIG. 2 shows a schematic diagram comprising a diametrically magnetizedmagnet and a magnetic angle sensor showing a magnetic target fieldvector and a disturbance field vector;

FIG. 3 shows a diametrically magnetized magnet that is arrangedrotatably around a rotation axis;

FIG. 4 shows the magnet illustrated in FIG. 3, where two angle sensorsare placed on the rotation axis at different distances from the magnet;

FIG. 5 shows the angle sensors illustrated in FIG. 4 from a differentperspective indicating the rotational angle errors due to a disturbancefield; and

FIG. 6 shows an example arrangement of a dual-sensor-package.

DETAILED DESCRIPTION

Examples described herein in particular refer to magnetic angle sensors,where a permanent magnet is attached to a rotatable shaft and a magneticfield sensor is placed on the rotation axis and adjacent to the magnet.The magnetic angle sensor detects the rotatable magnetic field, whichpoints in diametric direction, and therefrom it infers the rotationalposition of the shaft.

Various sensors can be used, e.g., an anisotropic magneto-resistor(AMR), a giant magneto-resistor (GMR), a tunneling magneto-resistor(TMR), Hall-effect devices (e.g., Hall plates, vertical Hall-effectdevices) or magnetic field-effect transistor (MAG-FET) (e.g.,split-drain MAG-FETs).

The embodiments provided herein use several angle sensors and combinetheir outputs to derive an angle estimation which is robust againstexternal disturbance fields.

This may be beneficial in harsh environments such as in a vehicle orcar, where external magnetic fields generated by current-rails in thevehicle influence the accuracy of the magnetic angle measurement. Thisbecomes particularly problematic in hybrid or electric cars whichcomprise a multitude of wires carrying high currents adjacent to or inthe vicinity of the sensor system.

FIG. 2 shows an schematic diagram comprising a diametrically magnetizedmagnet 201 and a magnetic angle sensor 202. The magnet 201 has amagnetic target field vector 203; also, a disturbance field vector 204is present. The disturbance field vector 204 superimposes with thetarget field vector 203 of the magnet 201 and generates an angle erroron the magnetic angle sensor 202.

FIG. 1 shows an example arrangement comprising a shaft 108 that rotatesaround a rotation axis 107. A magnet 109 is attached to the bottom ofthe shaft 108, wherein the magnet has a magnetization 110 inx-direction. Three angle sensors 101, 102 and 103 are arranged within amold body 111, which is arranged below the magnet 109. The distancebetween the magnet 109 and the mold body 111 may be in a range between 1mm and 3 mm. Each of the angle sensors 101 to 103 comprises a sensorelement 104 to 106. The angle sensors 101 to 103 are electricallyconnected to leads 113 a, 113 b via bond wires 115, wherein the moldbody 111 is connected via the leads 113 a, 113 b to a printed circuitboard 114.

The magnetic angle sensors 101 to 103 are of a type “perpendicular anglesensor”, which means that they respond to the rotation angle of theshaft, wherein the magnetic field component affects a sensing surface ofthe respective angle sensor that is perpendicular to the rotation axis.They are arranged stacked to each other, so that the gravity centers oftheir sensor elements 104 to 106 are substantially located on therotation axis 107 and they are at three different distances from themagnet 109 (i.e. at different z-positions). The angle sensor 101 and theangle sensor 102 are separated by a distance element 112, wherein theangle sensor 102 is located on top of a die paddle 113 c. The anglesensor 103 is mounted below the die paddle 113 c, wherein the sensorelements 105, 106 are arranged on opposite sides of the angle sensors102, 103.

The angle sensor 101 detects an angle φ₁. The sensor element 104 of theangle sensor 101 is at an axial position z₁.

The angle sensor 102 detects an angle φ₂. The sensor element 105 of theangle sensor 102 is at an axial position z₂.

The angle sensor 103 detects an angle φ₃. The sensor element 106 of theangle sensor 103 is at an axial position z₃.

It is noted that each of the angle sensors 101 to 103 may comprise atleast one sensor element 104 to 106.

It is noted that each angle sensor may comprise two vertical Halldevices (also referred to as vertical Hall effect devices). In anexample embodiment, a first vertical Hall device is oriented such thatit merely detects magnetic field components in a first direction (e.g.,in x-direction, whereas magnetic field components in y- and z-directionare not detected by the first vertical Hall device). A second verticalHall device is oriented such that it merely detects magnetic fieldcomponents in a second direction, which is different from the firstdirection (e.g., in y-direction, whereas magnetic field components in x-and z-direction are not detected by the second vertical Hall device).The angle sensor determines a signal which corresponds to the arctan ofthe magnetic fields B_(x) and B_(y), i.e. arctan₂ (B_(x), B_(y)). Thisis equivalent to the angle between the magnetic field with a vanishingB_(z)-component and a positive x-axis. If the B_(z)-component of themagnetic field is set zero, a projection of the magnetic fieldperpendicular to the rotation axis can be obtained, which is parallel tothe z-axis. This projection is also called diametric magnetic field.

It is an option that each angle sensor may comprise two Wheatstonebridges of magneto-resistive resistors. One bridge provides a signalthat is proportional to the sine of an angle between the diametricmagnetic field and the x-axis. The other bridge provides a signal thatis proportional to the cosine of this angle. The angle sensor may thusprovide the signal that corresponds to the arctan of this sine andcosine, i.e. arctan₂ (cos, sin).

Each bridge comprises four resistors in an Wheatstone bridgearrangement. In case GMRs or TMRs are used, the resistors of the maindiagonal of the sine bridge comprise a pinned layer, which is magnetizedin positive y-direction. The resistors of the secondary diagonal of thesine bridge comprise a pinned layer, which is magnetized in negativey-direction. The resistors of the main diagonal of the cosine bridgecomprise a pinned layer, which is magnetized in positive x-direction andthe resistors of the secondary diagonal of the cosine bridge comprise apinned layer, which is magnetized in negative x-direction.

In case AMR sensors are used, the signals of the bridges areproportional to cos(2φ) and sin(2φ) with φ being the angle between thediametric magnetic field component and the positive x-axis. Theresistors of the cosine bridge show a current flow in x-direction alongthe main diagonal and a current flow in y-direction along the secondarydiagonal (positive or negative does not matter in this case). Theresistors of the sine bridge show a current flow in x-direction plus 45degrees (clock-wise) along the main diagonal and a current flow inx-direction minus 45 degrees (counter-clock-wise) along the secondarydiagonal.

A diametric magnetic field on the rotation axis 107 at the axialposition z₁ which is generated by the rotatable magnet 109 amounts toB₁, which comprises the components B_(x1) and B_(y1) (theB_(z)-component is irrelevant). It is noted that “diametric” means aprojection of the magnetic field vector on the x-y-plane, i.e. a fieldvector with no or no significant z-portion.

A diametric magnetic field on the rotation axis 107 at the axialposition z₂ which is generated by the rotatable magnet 109 amounts tok₂·B₁, which comprises the components k₂·B_(x1) and k₂·B_(y1) (theB_(z)-component is irrelevant).

The diametric magnetic field on the rotation axis 107 at the axialposition z₃ which is generated by the rotatable magnet 109 amounts tok₃·B₁, which comprises the components k₃·B_(x1) and k₃·B_(y1) (theB_(z)-component is irrelevant).

Further, a homogeneous disturbance field Bd may be present comprisingthe components Bd_(x) and Bd_(y) (the B_(z)-component is irrelevant).

The following applies:

$\begin{matrix}{{\tan \; \phi_{1}} = \frac{B_{y\; 1} + {Bd}_{y}}{B_{x\; 1} + {Bd}_{x}}} & {{eq}.\mspace{14mu} (1)} \\{{\tan \; \phi_{2}} = \frac{{k_{2} \cdot B_{y\; 1}} + {Bd}_{y}}{{k_{2} \cdot B_{x\; 1}} + {Bd}_{x}}} & {{eq}.\mspace{14mu} (2)} \\{{\tan \; \phi_{3}} = \frac{{k_{3} \cdot B_{y\; 1}} + {Bd}_{y}}{{k_{3} \cdot B_{x\; 1}} + {Bd}_{x}}} & {{eq}.\mspace{14mu} (3)}\end{matrix}$

Hence, the rotational position φ0 of the shaft 108 amounts to:

$\begin{matrix}{{\tan \; \phi_{0}} = \frac{B_{y\; 1}}{B_{x\; 1}}} & {{eq}.\mspace{14mu} (4)}\end{matrix}$

Multiplying equation (1) with (Bx1+Bdx) leads to:

(B _(x1) +Bd _(x))·tan φ₁ =B _(y1) +Bd _(y); eq.  (5)

Multiplying equation (2) with (k₂·B_(x1)+Bd_(x)) leads to:

(k ₂ ·B _(x1) +Bd _(x))·tan φ₂ =k ₂ ·B _(y1) +Bd _(y); eq.  (6)

Multiplying equation (3) with (k₃·B_(x1)+Bd_(x)) leads to:

(k ₃ ·B _(x1) +Bd _(x))·tan φ₃ =k ₃ ·B _(y1) +Bd _(y). eq.  (7)

Subtracting equations (5) to (6) result in:

(B _(x1) +Bd _(x))·tan φ₁−(k ₂ ·B _(x1) +Bd _(x))·tan φ₂ =B _(y1) −k ₂·B _(y1). eq.  (8)

Subtracting equations (5) to (7) result in:

(B _(x1) +Bd _(x))·tan φ₁−(k ₃ ·B _(x1) +Bd _(x))·tan φ₃ =B _(y1) −k ₃·B _(y1). eq.  (9)

Equation (4) can be converted to:

B _(y1) =B _(x1)·tan φ₀

which allows replacing By1 in equations (8) and (9) leading to:

(B _(x1) +Bd _(x))·tan φ₁−(k ₂ ·B _(x1) +Bd _(x))·tan φ₂=(1−k ₂)·B_(x1)·tan φ₀; eq.  (10)

(B _(x1) +Bd _(x))·tan φ₁−(k ₃ ·B _(x1) +Bd _(x))·tan φ₃=(1−k ₃)·B_(x1)·tan φ₀. eq.  (11)

Separating Bdx at the left hand side of equations (10) and (11) leadsto:

Bd _(x)(tan φ₁−tan φ₂)=(1−k ₂)B _(x1) tan φ₀ −B _(x1) tan φ₁ +k ₂ B_(x1) tan φ₂; eq.  (12)

Bd _(x)(tan φ₁−tan φ₃)=(1−k ₃)B _(x1) tan φ₀ −B _(x1) tan φ₁ +k ₃ B_(x1) tan φ₃; eq.  (13)

A division of equations (12)/(13) and solving the result for tan φ0leads to:

$\begin{matrix}{{\tan \; \phi_{0}} = {\frac{\begin{pmatrix}{{( {{\tan \; \phi_{1}} - {\tan \; \phi_{3}}} )( {{k_{2}\tan \; \phi_{2}} - {\tan \; \phi_{1}}} )} -} \\{( {{\tan \; \phi_{1}} - {\tan \; \phi_{2}}} )( {{k_{3}\tan \; \phi_{3}} - {\tan \; \phi_{1}}} )}\end{pmatrix}}{( {{( {1 - k_{3}} )( {{\tan \; \phi_{1}} - {\tan \; \phi_{2}}} )} - {( {1 - k_{2}} )( {{\tan \; \phi_{1}} - {\tan \; \phi_{3}}} )}} )}.}} & {{eq}.\mspace{14mu} (14)}\end{matrix}$

It is noted that the arctan-function is not without ambiguity across360°. The arctan-function ranges only from −90° to +90°. In the examplesused, a range from −180° to +180° would be preferable. This can beachieved via the function arctan2(x,y), which is identical to thearctan(y/x), if x≧0. However, if x<0, the following applies:

${{\arctan_{2}( {x,y} )} = {{\arctan \frac{y}{x}} - \pi}},$

which is indicated in radians (rad). Hence, instead of equation (14),the following may apply:

φ₀=arctan₂(A, B)

wherein

A=(1−k ₃)cos φ₁ cos φ₃(sin φ₁ cos φ₂ sin φ₂ cos φ₁)−(1−k ₂)cos φ₁ cos φ₂(sin φ₁ cos φ₃−sin φ₃ cos φ₁);

B=(sin φ₁ cos φ₃−sin φ₃ cos φ₁)·(k ₂ sin φ₂ cos φ₁−sin φ₁ cos φ₂)−(sinφ₁ cos φ₂−sin φ₂ cos φ₁)·(k ₃ sin φ₃ cos φ₁−sin φ₁ cos φ₃).

The arctan applied to the right hand side of equation (14) provides therotation angle φ0. This computed rotation angle φ0 is no longer(significantly) affected and/or corrupted by the disturbance field. Theangle sensors 101 to 103 provide their data to be input in the aboveequation (14). Also, the numbers k2 and k3 are used, which can be fixednumbers that may depend on the ratios of magnetic field strengths at thepositions z2, z3 compared to the position z1. Advantageously, thepositions z1, z2 and z3 are located on the rotation axis 107. Hence,based on the system design, the positions of the sensors 101 to 103along the z-axis are known.

In case of significant axial play, this might affect the field strengthson the angle sensors 101 to 103, but the ratio of the field strength onthe angle sensor 102 over the field strength on the angle sensor 101(i.e. k2) and the ratio of the field strength on the angle sensor 103over the field strength on the angle sensor 101 (i.e. k3) changessignificantly less.

If the function of the absolute value of the diametric magnetic field Balong the rotation axis (i.e. the z-axis) is a linear function over z,the numbers k2 and k3 are constants even in case the magnet 109experiences axially shifts.

It is an option to utilize magnets that provide such linearrelationship. For example, a small stud hole may be drilled into thesurface of the magnet, in particular into the surface that faces theangle sensors 101 to 103 (in case all angle sensors are on the same sideof the magnet 109).

Each of the angle sensors 101 to 103 may have a sensitive plane that isperpendicular to the rotation axis 107. In case of AMR, GMR, TMR orvertical Hall angle sensors, the sensitive plane may be (substantially)identical to the main surface of the die, which accommodates the sensorelement(s).

The position of the sensor element 104 to 106 may thus be defined as anintersect point where the sensitive plane of the angle sensors 101 to103 intersects the rotation axis 107.

The sensor elements 104 to 106 respond to a projection of the magneticfield vector into the sensitive plane at these intersect points. If themagnet 109 rotates around the rotation axis 107, this projection rotatesas well, which results in two orthogonal magnetic field components Bx,By; the third magnetic field component Bz points out of the sensitiveplane and it may be omitted in a first approximation for these types ofangle sensors.

The diametric magnetic field strength may be denoted as:

√{square root over (B _(x) ² +B _(y) ²)},

which is the strength of the projection of the field vector into thesensitive plane.

With regard to the terminology used herein, the axial and the lateraldirection may be distinguished as follow: the axial direction is alongthe rotation axis 107 (z-axis); the lateral directions are perpendicularto the rotation axis, i.e., in the x-y-plane. Hence, there is aninfinite number of lateral directions and only one axial direction.

As an option, the angle sensor 101 may be arranged in a first package onthe top side of the printed circuit board 114 and the angle sensor 103may be arranged in a second package on the bottom side of the printedcircuit board 114. The angle sensor 102 may be arranged either withinthe first package or the second package.

It is noted that an increased reliability is another advantage of thesystem: the system allows obtaining three estimations of a rotationangle, i.e. φ1, φ2, φ3, which can be combined, e.g., for comparisonpurposes. For example, it may be decided that one of the angle sensor isdefective if it produces a rotation angle that is substantiallydifferent (e.g., exceeding a predefined threshold for a variationbetween the rotation angles) from the rotation angles detected by theother two angle sensors. The defect may be notified, e.g., as an alarm,and/or the result of the defective angle may no longer used; in suchexample scenario, the rotation angles from the other two (non-defective)angle sensors may be averaged and used for further processing.

It is also an advantage that the system is able to determine whether theangle sensors 101 to 103 are monotonously distributed. In case ofperfectly arranged angle sensors 101 to 103 and a homogeneous magneticdisturbance field, either:

φ₁>φ₂>φ₃

or

φ₁<φ₂<φ₃

applies (in a modulo-360°-scheme). If the angle sensors 101 to 103 arenot monotonously distributed, there is some error: Either the anglesensors 101 to 103 malfunction or the disturbance field is highlyinhomogeneous.

As an option, the system may check the monotony only if the differencesbetween the rotation angles φ1, φ2 and φ3 are above a predeterminedthreshold, which may be larger than an anticipated production spread.This avoids detecting an inhomogeneous distribution of angle sensorseven in case there is none.

By inserting the rotation angle φ0 in equations (12), (13) and (6), (7),the system is able to compute the ratios:

$\frac{{Bd}_{x}}{B_{x\; 1}}\mspace{14mu} {and}\mspace{14mu} {\frac{{Bd}_{y}}{B_{y\; 1}}.}$

Equation (12) or equation (13) can be used to calculate Bdx/Bx1 based onthe rotation angles φ1, φ2 and φ3. This result can be inserted inequation (6) or in equation (7) to calculate Bdy/By1.

It is in particular an option to determine:

$\begin{matrix}{\frac{\sqrt{{Bd}_{x}^{2} + {Bd}_{y}^{2}}}{\sqrt{B_{x\; 1}^{2} + B_{y\; 1}^{2}}},} & {{eq}.\mspace{14mu} (15)}\end{matrix}$

which is independent from the rotation angle and provides the ratio ofdisturbance field to target field (target field: the field of themagnet).

Bdx/Bx1 can be used to determine:

$\begin{matrix}{\frac{{Bd}_{x}}{\sqrt{B_{x\; 1}^{2} + B_{y\; 1}^{2}}} = {\frac{{{Bd}_{x} \cdot \cos}\; \phi_{0}}{B_{x\; 1}}.}} & {{eq}.\mspace{14mu} (16)}\end{matrix}$

Accordingly, Bdy/By1 can be used to determine:

$\begin{matrix}{\frac{{Bd}_{y}}{\sqrt{B_{x\; 1}^{2} + B_{y\; 1}^{2}}} = {\frac{{{Bd}_{y} \cdot \sin}\; \phi_{0}}{B_{y\; 1}}.}} & {{eq}.\mspace{14mu} (17)}\end{matrix}$

Both equations (16) and (17) can be combined to reach equation (15),i.e., equations (16) and equation (17) are both squared and then addedand subsequently the root is extracted from this addition. The valueprovided by equation (15) can be compared with a predetermined thresholdto indicate whether or not the disturbance field is within an acceptablerange.

Hence, the system can determine the amount of disturbance in relation tothe magnetic field of the magnet. This ratio can be compared with atleast one predefined limit and the system may issue an alarm if thedisturbance has become too large, which may lead to unreliable orinaccurate results.

According to an example, two angle sensors are used to derive therotation/angle information. However, the embodiments are not limitedthereto, and more than two angle sensors may be used, where each sensorgenerates angle information used to derive the final measurement (i.e.,a combined rotation angle).

The magnetic field of a magnet is strongly dependent on the distance ofthe sensor to the magnet. FIG. 3 shows a diametrically magnetized magnet301 that is arranged rotatably around a rotation axis 302. An ellipsewith an arrow 304 indicates a rotation of the magnet 301 around therotation axis 302.

A magnetic target field is indicated by arrows 303 a to 303 e, whereinthe size of the diametric magnetic field B decreases with an increasingdistance d from the magnet 301; this is also indicated by a decreasinglength of the arrows 303 a to 303 e. In other words, the lengths of thearrows 303 a to 303 e indicate the strength of the diametric magneticfield at an axial distance d from the magnet 301.

FIG. 4 shows the magnet 301 and the rotation axis 302 of FIG. 3, whereinan angle sensor 401 is placed on the rotation axis 302 at a distance difrom the magnet 301 and an angle sensor 402 is placed on the rotationaxis 302 at a distance d₂ from the magnet 301. In this example, themagnetic sensor elements are on top of the angle sensors 401 and 402.

In the presence of homogeneous disturbance fields, the angle sensors 401and 402 may sense different rotation angles due to their differingdistances d₁ and d₂ from the magnet 301, which result in differentsuper-positions of fields from the magnet and disturbance field.

It is noted that in FIG. 4 a coordinate system with x-y-z-axes is shown,wherein the rotation axis 302 is along the z-axis and the sensors 401,402 are arranged also in the x-y-plane.

FIG. 5 shows the angle sensors 401 and 402, wherein both sensorsexperience a disturbance field vector 503, which is assumed to be of thesame size for both angle sensors 401, 402. For the angle sensor 401, dueto the disturbance field vector 503, a magnetic field vector 504 of themagnet 301 is skewed into a resulting magnetic field vector 505 leadingto a rotation angle error 506. For the angle sensor 402, due to thedisturbance field vector 503, a magnetic field vector 507 of the magnet301 is skewed into a resulting magnetic field vector 508 leading to arotation angle error 509.

Since the angle sensor 401 is closer to the magnet 301 than the anglesensor 402, the disturbance field vector 503 has a larger impact on themagnetic field vector 507 than on the magnetic field vector 504, whichresults in the rotation angle error 509 being larger than the rotationangle error 506.

Based on this example scenario, the actual rotation angle may bedetermined or approximated and even the size of the disturbance fieldmay be determined or approximated. In order to achieve this, the fieldsize of the magnet 301 is to be known.

It is noted that the coordinate system introduced in FIG. 4 is alsoshown in FIG. 5 to indicate the orientation of the angle sensors 401 and402.

A linear combination of the rotation angles obtained by these two anglesensors may result in a rotation angle that is robust againstdisturbances.

The magnet 301 may point into a direction that is associated with 0° (asa starting reference). The angle sensors 401 and 402 may produce thefollowing rotation angles:

${\alpha_{1} = {\arctan \frac{{Bd}_{n}}{B_{1} + {Bd}_{p}}}},{\alpha_{2} = {\arctan \frac{{Bd}_{n}}{B_{2} + {Bd}_{p}}}},$

where: α1 is the rotation angle determined by the angle sensors 401; α2is the rotation angle determined by the angle sensors 402; Bdn is thediametric disturbance field component that is normal to the field of themagnet; Bdp is the diametric disturbance field component that isparallel to the field of the magnet; B1 is the diametric field of themagnet that affects the sensor 401; and B2 is the diametric field of themagnet that affects the sensor 402.

In case of a small disturbance field Bd the following applies:

${\alpha_{1} \approx \frac{{Bd}_{n}}{B_{1}}},{{\alpha_{2} \approx \frac{{Bd}_{n}}{B_{2}}} = {\frac{{Bd}_{n}}{B_{1}} \cdot {\frac{B_{1}}{B_{2}}.}}}$

A rotation angle αbest-guess may be determined as follows:

${\alpha_{{best}\text{-}{guess}} = {{\alpha_{1} + {c \cdot ( {\alpha_{1} - \alpha_{2}} )}} = {{\frac{{Bd}_{n}}{B_{1}} + {c \cdot ( {\frac{{Bd}_{n}}{B_{1}} - {\frac{{Bd}_{n}}{B_{1}} \cdot \frac{B_{1}}{B_{2}}}} )}} = {\frac{{Bd}_{n}}{B_{1}} \cdot ( {1 + {c \cdot ( {1 - \frac{B_{1}}{B_{2}}} )}} )}}}},$

where c is a compensation factor.

The rotation angle αbest-guess should be 0°, because the magnet pointsin this 0° direction.

This results in:

${{\frac{{Bd}_{n}}{B_{1}} \cdot ( {1 + {c \cdot ( {1 - \frac{B_{1}}{B_{2}}} )}} )} = 0},{c = {\frac{1}{\frac{B_{1}}{B_{2}} - 1}.}}$

An algorithm may be used to determine α_(best-guess)=α₁+c·(α₁−α₂).

The algorithm may use the constant c, which is given by the lastequation and which depends only on the ratio of fields of the magnet onboth angle sensors. Although the formula has been derived with theassumption of a special rotational position φ=0°, it works for allrotational positions.

B1/B2 may for example amount to 1.5. This results in c=2 and

α_(best-guess)=α₁+2·(α₁−α₂)=3α₁−2α_(2.)

FIG. 6 shows an example arrangement of a dual-sensor-package. A top die601 is arranged on top of a leadframe 600, wherein an insulating glue605 is arranged between the top die 601 and the leadframe 600. The topdie 601 comprises a sensor element 602 and the top die 601 iselectrically connected to the leadframe 600 via bond wires 603.

A bottom die 606 is arranged on the bottom of the leadframe 600, whereinan insulating glue 609 is arranged between the bottom die 606 and theleadframe 600. The bottom die 606 comprises a sensor element 607 and thebottom die 606 is electrically connected to the leadframe 600 via bondwires 608. In an example use case, the sensing elements 602 and 607 arespaced apart from each other by less than 600 μm.

In this dual-the setup the magnetic sensor elements 602 and 607 are ontop of each other and both sensor elements 602, 607 are directly aboveeach other so that they can be placed both on the rotation axis if thechips are orthogonal to the rotation axis.

A microcontroller (not shown in FIG. 6) can be connected to theleadframe 600 (and thereby to the sensor elements 602 and 607) to readthe rotation angles and to perform the compensation to determine thecombined rotation angle as proposed herein.

Advantageously, this approach allows for rotation angle measurementsthat are robust against disturbance fields.

The arrangement shown in FIG. 6 can be used to be placed below themagnet 301 of FIG. 4. In this case, the angle sensor 401 corresponds tothe sensor element 602 and the angle sensor 402 corresponds to thesensor element 607. It is in particular an option to place the anglesensors 401 and 402 on separate or opposite sides of a printed circuitboard (PCB) to increase the distance between the angle sensors (and theangle sensor elements). In this case, the angle sensors 401 and 402 mayhave packages on their own and each of the angle sensors 401 and 402 maycomprise at least one angle sensor element. The packages may be placedon opposing sides of the printed circuit board (similar to what isdescribed above with regard to FIG. 1).

It is also an option that the corrected rotation angle is calculated byone of the angle sensors if both angle sensors are integrated in apackage. For example, a first angle sensor can be used for determiningthe corrected rotation angle in case the first and a second angle sensorare connected by bond wires or by leads: Hence, the first angle sensorobtains the data from the second angle sensor and computes the corrected(e.g., compensated) rotation angle based on the data determined by thefirst and the second angle sensors. In such scenario, a microcontrollermay be provided for reading such corrected rotation angle from the firstsensor.

Hence, this example utilizes the fact that the diametric field from themagnet is different at different distances from the magnet; placingangle sensors at different distances from the magnet allows for a robustsetup to at least partially compensate magnetic disturbance fields.

The devices and methods provided herein may in particular be based on atleast one of the following embodiments. In particular, combinations ofthe following features of the following embodiments could be utilized inorder to reach a desired result. The features of the method could becombined with any feature(s) of the device, apparatus or system or viceversa.

A magnetic angle sensor device is provided including: a shaft rotatablearound a rotation axis; a magnetic field source, wherein the magneticfield source is connected to the shaft; a first magnetic angle sensorand a second magnetic angle sensor, where the first magnetic anglesensor generates a first signal that represents first angle based on afirst diametric magnetic field applied to the first magnetic anglesensor, where the second magnetic angle sensor generates a second signalthat represents a second angle based on a second diametric magneticfield applied to the second magnetic angle sensor, and a combinedrotation angle is determined based on the first signal and on the secondsignal.

A combining circuit (e.g., combining logic, a processor, and/or amicrocontroller) may be operatively connected to the first magneticangle sensor and the second magnetic angle sensor, and configured toreceive the first signal and the second signal, and determine thecombined rotation angle based on the first signal and on the secondsignal. The processor may be configured to generate a measurement signalthat represents the combined rotation angle. The processor may use themeasurement signal representing the combined rotation angle for furtherprocessing and/or may output the measurement signal to another device.

The magnetic field source is in particular rigidly attached to theshaft.

Each of the magnetic angle sensor may be a magnetic field angle sensor.

The magnetic field is a vector at each point. This vector can bedecomposed into a vector parallel to the rotation axis and a vectororthogonal to the rotation axis. The latter is the diametric magneticfield.

If a chip is oriented with its major surface perpendicular to therotation axis and magneto-resistive elements are sputtered to its majorsurface, these elements respond to diametric magnetic fields. The samechip may comprise vertical Hall effect devices, which also respond todiametric magnetic field components. Conversely, if Hall plates areoriented perpendicular to the rotation axis they respond to the axialmagnetic field component.

In practice the chip may be tilted by a few degrees due to assemblytolerances. If the major surface of a chip is not exactly perpendicularto the rotation axis, the magneto-resistive elements on its majorsurface respond mainly to the diametric magnetic field component butalso a little bit to the axial magnetic field component. As long as thenormal to the major chip surface deviates by less than 10° from thedirection of the rotation axis, the magneto-resistive elements stillessentially see the diametric magnetic field components and onlynegligible axial magnetic field components.

As an option, Vertical Hall effect devices may be used, because theyalso detect predominately the diametric magnetic field components, i.e.,the magnetic field components parallel to the major chip surface, whichis essentially orthogonal to the rotation axis.

The example presented may be particularly robust against magneticdisturbance fields.

According to one or more embodiments, the first magnetic angle sensordetermines/generates the first signal that represents the first anglebetween the first diametric magnetic field applied to the first magneticangle sensor and a first reference direction, and the second magneticangle sensor determines/generates the second signal that represents thesecond angle between the second diametric magnetic field applied to thesecond magnetic angle sensor and a second reference direction.

In an embodiment, the first reference direction and the second referencedirection are the same.

In an embodiment, the magnetic angle sensor device include a thirdmagnetic angle sensor, wherein the third magnetic angle sensordetermines/generates a third signal that represents a third angle basedon a third diametric magnetic field applied to the third magnetic anglesensor, and the combined rotation angle is determined based on the firstsignal, the second signal, and the third signal.

It is an option that more than three magnetic angle sensors are providedto determine the combined rotation angle.

In an embodiment, the third magnetic angle sensor determines the thirdsignal that represents the third angle between the third diametricmagnetic field applied to the third magnetic angle sensor and a thirdreference direction.

In an embodiment, at least two out of the following are the same: thefirst reference direction; the second reference direction; and the thirdreference direction.

In an embodiment, the magnetic field source includes at least onepermanent magnet.

In an embodiment, the magnetic angle sensors are located at differentz-positions (e.g., distances) from the magnetic field source, whereineach z-position is defined as a perpendicular dropped from the positionof the magnetic angle sensor onto the rotation axis.

The magnetic field source has a minimum distance d_(min) to the nearestmagnetic angle sensor. A distance between this magnetic angle sensor andany other magnetic angle sensor may in particular be equal to or largerthan ⅕ d_(min).

In an embodiment, each of the magnetic angle sensors includes at leastone magnetic sensor element that is arranged substantially on therotation axis or in particular spaced apart from the rotation axis byless than 1 mm.

It may be an option that the magnetic angle sensor includes a pluralityof magnetic sensor elements. As not all magnetic sensor elements may bearranged on the very same spot, the magnetic sensor elements may bearranged adjacent to the rotation axis, in particular in a symmetricalpattern around the rotation axis. It is also an option to choose asomewhat asymmetrical pattern arranging at least two magnetic sensorelements around the rotation axis. In such scenario, the magnetic anglesensor may determine an angle slightly off the rotation axis, e.g., by0.1 mm to 0.2 mm (e.g., up to 0.2 mm). Such positioning, however, isalso covered by the term “substantially on the rotation axis”.

In an embodiment, each of the magnetic angle sensors includes at leasttwo magnetic sensor elements that are arranged such that the angle ofthe diametric field vector on the rotation axis is measured.

In an embodiment, each of the two magnetic angle sensors includes amagnetic sensor element, where at least one magnetic sensor element permagnetic angle sensor is arranged at a different distance from themagnetic field source.

Hence, the magnetic field provided by the magnetic field source may havea different impact on each of the magnetic angle sensors, i.e., on atleast one of the magnetic sensor elements of the magnetic angle sensors.

In an embodiment, any of the signals includes two signal components, inparticular a sine signal component and a cosine signal component.

For example, each of the magnetic angle sensors may provide a signalcomprising a sine signal component and a cosine signal component.

In an embodiment, the magnetic angle sensors are arranged such that thediametric magnetic field strengths acting on the magnetic angle sensorscaused by the magnetic field source are mutually different.

It is noted that the magnetic angle sensors may be arranged such thatthe diametric magnetic field strengths acting on the magnetic anglesensors caused by the magnetic field source are mutually different by atleast 10%.

In an embodiment, the diametric magnetic fields acting on the magneticangle sensors are mutually parallel or mutually antiparallel.

In an embodiment, the device further includes a combining circuit, whichcombines the signals provided by the magnetic angle sensors to determinethe combined rotation angle.

The combining circuit may be arranged with either one of the magneticangle sensors or it may be arranged externally. The combining may be inparticular performed by a processor or microcontroller.

The combining circuit may combine the first signal and the second signalor the first, the second, and the third signal to derive the combinedrotation angle.

The combined rotation angle is an output signal that is indicative ofthe rotational position of the shaft.

In an embodiment, the combined rotation angle is determined as a linearcombination comprising the first signal and the second signal.

In an embodiment, the linear combination includes coefficients thatdepend on a ratio of the diametric magnetic fields of the magnetic fieldsource onto the magnetic angle sensors.

In an embodiment, the linear combination includes coefficients thatdepend only on a ratio of the diametric magnetic fields of the magneticfield source onto the magnetic angle sensors.

In an embodiment, the combined rotation angle is determined based on adistance of the magnetic angle sensors from the magnetic field source.

For example, the combined rotational angle is determined based on theratio of the diametric magnetic fields on the second versus the firstmagnetic angle sensor and on the third versus the first magnetic anglesensor (in case of three magnetic angle sensors).

The combined rotation angle may in particular be determined indirectlybased on the distance of the magnetic angle sensors from the magneticfield source.

According to one or more embodiments, at least two of the magnetic anglesensors are on two different substrates, where a major surface of atleast one substrate is perpendicular or substantially perpendicular tothe rotation axis.

In an embodiment, the at least two substrates are located on therotation axis of the shaft.

In an embodiment, the at least two substrates are attached to a singleleadframe.

According to one or more embodiments, at least two of the magnetic anglesensors are on the same substrate and the major surface of thissubstrate is orthogonal or substantially orthogonal to the rotation axisof the shaft.

According to one or more embodiments, each of the magnetic angle sensorsincludes at least one out of the following group of sensor elements: ananisotropic magneto-resistor (AMR); a giant magneto-resistor (GMR); atunneling magneto-resistor (TMR); a Vertical Hall effect device; a Hallplate; and/or a MAG-FET.

The magnetic angle sensors may be of different technologies (i.e.,different types of sensors) to increase the robustness and diversity ofthe system. For example, one of the angle sensors may be a TMR andanother other angle sensor may be an AMR or a Vertical Hall sensor.Using different technologies may mitigate the risk that both anglesensors fail under severe conditions.

According to one or more embodiments, a method is provided fordetermining a combined rotation angle of a shaft, where the shaft isarranged rotatably around a rotation axis and wherein a magnetic fieldsource is connected to the shaft. The method includes: determining by afirst magnetic angle sensor a first signal that represents a first anglebased on a first diametric magnetic field from the magnetic field sourceapplied to the first magnetic angle sensor; determining by a secondmagnetic angle sensor a second signal that represents a second anglebased on a second diametric magnetic field from the magnetic fieldsource applied to the second magnetic angle sensor; and determining thecombined rotation angle based on the first signal and on the secondsignal.

In an embodiment, the method further includes determining by a thirdmagnetic angle sensor a third signal that represents a third angle basedon a third diametric magnetic field from the magnetic field sourceapplied to the third magnetic angle sensor; and determining the combinedrotation angle based on the first signal, the second signal and thethird signal.

Also, a computer program product is provided that is directly loadableinto a memory of a digital processing device, including software codeportions that enable the digital processing device to perform one ormore methods described herein.

Further, a computer-readable medium is provided havingcomputer-executable instructions adapted to cause a computer system toperform one or more methods described herein.

In one or more examples, the functions described herein may beimplemented at least partially in hardware, such as specific hardwarecomponents or a processor. More generally, the techniques may beimplemented in hardware, processors, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium and executed by a hardware-based processingunit. Computer-readable media may include computer-readable storagemedia, which corresponds to a tangible medium such as data storagemedia, or communication media including any medium that facilitatestransfer of a computer program from one place to another, e.g.,according to a communication protocol. In this manner, computer-readablemedia generally may correspond to (1) tangible computer-readable storagemedia which is non-transitory or (2) a communication medium such as asignal or carrier wave. Data storage media may be any available mediathat can be accessed by one or more computers or one or more processorsto retrieve instructions, code and/or data structures for implementationof the techniques described in this disclosure. A computer programproduct may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium, i.e., a computer-readable transmission medium.For example, if instructions are transmitted from a website, server, orother remote source using a coaxial cable, fiber optic cable, twistedpair, digital subscriber line (DSL), or wireless technologies such asinfrared, radio, and microwave, then the coaxial cable, fiber opticcable, twisted pair, DSL, or wireless technologies such as infrared,radio, and microwave are included in the definition of medium. It shouldbe understood, however, that computer-readable storage media and datastorage media do not include connections, carrier waves, signals, orother transient media, but are instead directed to non-transient,tangible storage media. Disk and disc, as used herein, includes compactdisc (CD), laser disc, optical disc, digital versatile disc (DVD),floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

Instructions may be executed by one or more processors, such as one ormore central processing units (CPU), digital signal processors (DSPs),general purpose microprocessors, application specific integratedcircuits (ASICs), field programmable logic arrays (FPGAs), or otherequivalent integrated or discrete logic circuitry. Accordingly, the term“processor,” as used herein may refer to any of the foregoing structureor any other structure suitable for implementation of the techniquesdescribed herein. In addition, in some aspects, the functionalitydescribed herein may be provided within dedicated hardware and/orsoftware modules configured for encoding and decoding, or incorporatedin a combined codec. Also, the techniques could be fully implemented inone or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a single hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Although various example embodiments of the invention have beendisclosed, it will be apparent to those skilled in the art that variouschanges and modifications can be made which will achieve some of theadvantages of the invention without departing from the spirit and scopeof the invention. It will be obvious to those reasonably skilled in theart that other components performing the same functions may be suitablysubstituted. It should be mentioned that features explained withreference to a specific figure may be combined with features of otherfigures, even in those cases in which this has not explicitly beenmentioned. Further, the methods of the invention may be achieved ineither all software implementations, using the appropriate processorinstructions, or in hybrid implementations that utilize a combination ofhardware logic and software logic to achieve the same results. Suchmodifications to the inventive concept are intended to be covered by theappended claims.

What is claimed is:
 1. Magnetic angle sensor device comprising: a shaftrotatable around a rotation axis; a magnetic field source coupled to theshaft; a first magnetic angle sensor configured to generate a firstsignal that represents a first angle based on a first diametric magneticfield from the magnetic field source applied to the first magnetic anglesensor; a second magnetic angle sensor configured to generate a secondsignal that represents a second angle based on a second diametricmagnetic field from the magnetic field source applied to the secondmagnetic angle sensor; and a combining circuit configured to determine acombined rotation angle based on the first signal and on the secondsignal.
 2. The device according to claim 1, wherein: the first magneticangle sensor generates the first signal that represents the first anglebetween the first diametric magnetic field applied to the first magneticangle sensor and a first reference direction, and the second magneticangle sensor generates the second signal that represents the secondangle between the second diametric magnetic field applied to the secondmagnetic angle sensor and a second reference direction.
 3. The deviceaccording to claim 2, wherein the first reference direction and thesecond reference direction are the same.
 4. The device according toclaim 1, further comprising: a third magnetic angle sensor configured togenerate a third signal that represents a third angle based on a thirddiametric magnetic field from the magnetic field source applied to thethird magnetic angle sensor, wherein the combining circuit is configuredto determine the combined rotation angle based on the first signal, thesecond signal and the third signal.
 5. The device according to claim 4,wherein the third magnetic angle sensor generates the third signal thatrepresents the third angle between the third diametric magnetic fieldapplied to the third magnetic angle sensor and a third referencedirection.
 6. The device according to claim 5, wherein at least two outof the following are the same: the first reference direction; the secondreference direction; and the third reference direction.
 7. The deviceaccording to claim 1, wherein the magnetic field source comprises atleast one permanent magnet.
 8. The device according to claim 1, whereinthe first magnetic angle sensor and the second magnetic angle sensor arelocated at different z-positions from the magnetic field source, whereina z-position of the first magnetic angle sensor is defined as aperpendicular dropped from a position of the first magnetic angle sensoronto the rotation axis, and a z-position of the second magnetic anglesensor is defined as a perpendicular dropped from a position of thesecond magnetic angle sensor onto the rotation axis.
 9. The deviceaccording to claim 1, wherein each of the first magnetic angle sensorand the second magnetic angle sensor comprises at least one magneticsensor element that is arranged substantially on the rotation axis,spaced apart from the rotation axis by less than 1 mm.
 10. The deviceaccording to claim 1, wherein: the first magnetic angle sensor comprisesat least two magnetic sensor elements that are arranged such that thefirst angle of a diametric field vector on the rotation axis ismeasured, and the second magnetic angle sensor comprises at least twomagnetic sensor elements that are arranged such that the second angle ofa diametric field vector on the rotation axis is measured.
 11. Thedevice according to claim 1, wherein the first magnetic angle sensorcomprises a first magnetic sensor element and the second magnetic anglesensor comprises a second magnetic sensor element, the first magneticsensor element and the second magnetic sensor element being arranged atdifferent distances from the magnetic field source.
 12. The deviceaccording to claim 1, wherein each of the first signal and the secondsignal comprises a sine signal component and a cosine signal component.13. The device according to claim 1, wherein each of the first magneticangle sensor and the second magnetic angle sensor are arranged such thata strength of the first diametric magnetic field acting on the firstmagnetic angle sensor is mutually different from a strength of thesecond diametric magnetic field acting on the second magnetic anglesensor.
 14. The device according to claim 12, wherein the first and thesecond diametric magnetic fields acting on the first and the secondmagnetic angle sensors, respectively, are mutually parallel or mutuallyantiparallel.
 15. The device according to claim 1, wherein the combiningcircuit is configured to determine the combined rotation angle as alinear combination comprising the first signal and the second signal.16. The device according to claim 15, wherein the linear combinationcomprises coefficients that depend on a ratio of the first and thesecond diametric magnetic fields of the magnetic field source onto thefirst and the second magnetic angle sensors, respectively.
 17. Thedevice according to claim 15, wherein the linear combination comprisescoefficients that depend only on a ratio of the first and the seconddiametric magnetic fields of the magnetic field source onto the firstand the second magnetic angle sensors, respectively.
 18. The deviceaccording to claim 1, wherein the combining circuit is configured todetermine the combined rotation angle based on distances of the firstand the second magnetic angle sensors from the magnetic field source.19. The device according to claim 1, wherein the first and the secondmagnetic angle sensors are arranged on two different substrates, andwherein a major surface of at least one of the two different substratesis perpendicular or substantially perpendicular to the rotation axis.20. The device according to claim 19, wherein the two differentsubstrates are located on the rotation axis of the shaft.
 21. The deviceaccording to claim 19, wherein the two different substrates are attachedto a single leadframe.
 22. The device according to claim 1, wherein thefirst and the second magnetic angle sensors are arranged on a samesubstrate and a major surface of the substrate is orthogonal orsubstantially orthogonal to the rotation axis of the shaft.
 23. A methodfor determining a combined rotation angle of a shaft, wherein the shaftis arranged rotatably around a rotation axis and wherein a magneticfield source is connected to the shaft, the method comprising:generating, by a first magnetic angle sensor, a first signal thatrepresents a first angle based on a first diametric magnetic field fromthe magnetic field source applied to the first magnetic angle sensor;generating, by a second magnetic angle sensor, a second signal thatrepresents a second angle based on a second diametric magnetic fieldfrom the magnetic field source applied to the second magnetic anglesensor; and determining the combined rotation angle based on the firstsignal and on the second signal.
 24. The method according to claim 23,further comprising: generating, by a third magnetic angle sensor, athird signal that represents a third angle based on a third diametricmagnetic field from the magnetic field source applied to the thirdmagnetic angle sensor; and determining the combined rotation angle basedon the first signal, the second signal and the third signal.